1. Field of the Invention
This invention relates to reducing disk flutter in a disk drive by having apertures near the ID (“inner diameter”) of a disk stack for allowing airflow to pass though the apertures when the disks are rotating.
2. Description of the Prior Art and Related Information
A huge market exists for disk drives such as hard disk drives for mass-market host computer systems such as servers, desktop computers, and laptop computers. To be competitive in this market, a hard disk drive must be relatively inexpensive, and must accordingly embody a design that is adapted for low-cost mass production. In addition, it must provide substantial capacity, rapid access to data, and reliable performance. Numerous manufacturers compete in this huge market and collectively conduct substantial research and development, at great annual cost, to design and develop innovative hard disk drives to meet increasingly demanding customer requirements.
Each of numerous contemporary mass-market hard disk drive models provides relatively large capacity, often in excess of 40 gigabytes per drive. Nevertheless, there exists substantial competitive pressure to develop mass-market hard disk drives that have even higher capacities and that provide rapid access. Another requirement to be competitive in this market is that the hard disk drive must conform to a selected standard exterior size and shape often referred to as a “form factor.” Generally, capacity is desirably increased without increasing the form factor or the form factor is reduced without decreasing capacity.
Satisfying these competing constraints of low-cost, small size, high capacity, and rapid access requires innovation in each of numerous components and methods of assembly including methods of assembly of various components into certain subassemblies. Typically, the main assemblies of a hard disk drive are a head disk assembly and a printed circuit board assembly.
The head disk assembly includes an enclosure including a disk drive base and a disk drive cover, at least one disk having at least one recording surface, a spindle motor for causing each disk to rotate, and an actuator arrangement. The printed circuit board assembly includes circuitry for processing signals and controlling operations. Actuator arrangements can be characterized as either linear or rotary; substantially every contemporary cost-competitive small form factor drive employs a rotary actuator arrangement.
In a typical disk drive, the rotating disks generate airflow within the interior of the head disk assembly. Such airflow creates an excitation force which affects track following by a respective head over a respective disk surface. This excitation force is caused by the spatiotemporal fluctuation of pressure generated mainly by the disturbance of airflow onto a rotating disk and an actuator arm. The airflow may include secondary airflows which move upward and downward in a longitudinal direction around the ID and OD (“outer diameter”) of a disk. These secondary airflows impact disk vibration (“disk flutter”) the most. The impact of the secondary airflows around the OD may be lessened with a tight shroud. However, a need remains to lessen the adverse effects of secondary airflows near the ID of the rotating disks.